It is commonly believed that Google bought YouTube for $1.6 billion because the wildly popular video-sharing site represented a great way for the search giant to expand into video advertising.

It turns out the site could bring an even bigger benefit to the Mountain View company: It may provide a way for Google to easily and legally amass the world's biggest database of film and video - a database it could use to refine ways to search that kind of material.

Google confirmed Tuesday it would begin testing a system that would allow copyright holders to automatically remove unauthorized content from YouTube. Disney, Time Warner and some unidentified content owners will be participating, which will start next month.

"What we are trying to do is get this to work for YouTube's entire library," said spokesman Ricardo Reyes.